I would like to measure gas production in a small closed system, i.e. 40 ml tube with PTFE septum. I am wondering if it is more appropriate to continually sample from one tube over time and simply replace the gas I took from the tube with fresh air to maintain the same pressure OR should I prepare a vial for each time point so that I am only sampling the vial once.
What is the gas production rate (volume/time)? What is the sample volume needed for analysis? Will you be detecting using direct reading continuous sensor or is a discrete sample processed for analysis?
If the main gas is CO2 then you get 1 vol for each C atom used, or one vol when you consume one of O2. So you can sample and replace on that basis, but you are entirely reliant on the quality of the measures in terms of maintenance. So personally I would not like to take this too far unless you set up a set of tubes with different concentrations of CO2, and no gas producing medium, as 'controls'.
Hi Martha,
The vial would contain a system that produces chlorine dioxide. Reported rates with this same system have been 0.1 to 3.5 mg/hr over 25 hr period. The gas would be measured with a spectrophotometer. chlorine dioxide would be sampled through a mininert valve and hypodermic needle then dissolved in water for measurement.
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